1. Field of the Invention
This invention relates in general to inter-process communication, and more particularly to a method, apparatus and program storage device for providing non-blocking, minimum threaded two-way messaging.
2. Description of Related Art
Today business and personal activities generate an astonishing amount of electronic information that must be managed. Such management involves transmitting, receiving, processing, and storing electronic data. Data processing systems with multiple input/output (I/O) storage subsystems have been developed to manage this large volume of data. Data processing systems with multiple input/output (I/O) storage subsystems generally have multiple independent communication paths between at least one processor and each storage system. A typical data processing system includes clients that have an application program and an operating system. Further, in a typical data processing system, clients request data that is stored in various types of storage devices via at least one storage controller. High availability is provided by redundancy of the storage subsystems, multiple I/O channels, multiple controller paths in the storage controller, and multiple communication links between the storage controller and the storage devices. However, such system designs cannot guarantee delivery of data at specified service levels.
The requirement for service level agreements has created a demand for accountability that transcends enterprise and service provider environments. A Service Level Agreement (SLA) is a contract between a network service provider and a customer that specifies, usually in measurable terms, what services the network service provider will furnish. IT departments in major enterprises have adopted the idea of writing a Service Level Agreement so that services for their customers (users in other departments within the enterprise) can be measured, justified, and perhaps compared with those of outsourcing network providers. These concepts are applicable to the storage system environment.
Nevertheless, service providers must prove the value of services being delivered, particularly in light of the fact that these services are often obtained at a premium price. Companies are investing hundreds of billions of dollars in technology in order to become even more competitive. To stay in business, a company's ability to transact business cannot be impeded because a database server is out of disk space. As soon as a piece of the IT infrastructure fails, critical business operations begin to suffer; so, it is crucial that IT organizations keep these indispensable operations functioning.
Accordingly, storage can't be an afterthought anymore because too much is at stake. Two new trends in storage are helping to drive new investments. First, companies are searching for more ways to efficiently manage expanding volumes of data and make that data accessible throughout the enterprise—this is propelling the move of storage into the network. Second, the increasing complexity of managing large numbers of storage devices and vast amounts of data is driving greater business value into software and services.
This is where a Storage Area Network (SAN) enters the arena. A SAN consists of a communication infrastructure, which provides physical connections; and a management layer, which organizes the connections, storage elements, and computer systems so that data transfer is secure and robust. The term SAN is usually (but not necessarily) identified with block I/O services rather than file access services. It can also be a storage system consisting of storage elements, storage devices, computer systems, and/or appliances, plus all control software, communicating over a network. Thus, a SAN is a high-speed network that allows the establishment of direct connections between storage devices and processors (servers) within the distance supported by a high-speed data link such as Fibre Channel. The SAN can be viewed as an extension to the storage bus concept, which enables storage devices and servers to be interconnected using similar elements as in local area networks (LANs) and wide area networks (WANs): routers, hubs, etc. SANs offer simplified storage management, scalability, flexibility, availability, and improved data access, movement, and backup.
To provide quality-of-service guarantees over a SAN, priority access must be given to the programs that need a fast response time. Without service level agreements, low-priority jobs would be allowed to take up a storage system's time when those jobs could be postponed a few fractions of a second.
A centralized server is used to provide SLA in a SAN infrastructure. The centralized server accumulates SLAs on storage performance commitments and produces real-time monitoring display on clients. This centralized server is referred to as a SLA server. The SLA server connects to multiple I/O service agents that reside in separate virtualization engines (processors) placed between application hosts and storage subsystems. Such agents are called performance gateways. An I/O performance gateway is disposed between multiple application hosts and multiple physical storage subsystems The I/O performance gateways intercept I/O operations, send statistic data to the SLA server and take requests from the SLA server to throttle I/O operations when necessary. In such an environment, a reasonable large number of application hosts commonly share multiple storage subsystems.
The SLA server needs to control multiple gateways concurrently by quickly accessing the SLA database and analyzing the data against SLAs and policies in a parallel manner. The monitoring and throttling of block I/O operations is provided by inter-process communications. If the message passing from the SLA server to multiple I/O service agents becomes a bottleneck, the system will fail to satisfy the SLAs and therefore fail in its mission.
Data must be received from all the gateways within a certain poll interval. In prior systems, multiple threads are created and each thread is used to communicate with one agent. However, when lots of agents need to be managed or monitored by the system, a blocked send and receive on each agent will result delays due to two latencies: 1) write/send latency; and 2) read/receive latency.
It can be seen that there is a need for a method, apparatus and program storage device for providing send and receive operations in a non-blocking manner and using only a minimum number of threads to support all gateways for eliminating the latencies and providing real time responses.